Insert variable values in the middle of an string

In C#: If I want to create a message like this:
"Hi We have these flights for you: FlightA, B,C,D. Which one do you want"

where just the section in bold is dynamic and I pass its vale at run time, but its left and right part are fixed. I can create something like LeftMessage + those variables + RightMessage to create this.
But I was wondering if there is a way of doing it all at once? without the need to create two separate left and right messages?

for translation purposese I am putting those left and right messages inside string resources so now I have two separate string resource. So I wanted to see if there is a way to do it all at once?